Radio-frequency hybrid switch module

ABSTRACT

A small radio-frequency hybrid switch module is provided for switching between transmitted signals and received signals in plural frequency bands. This module includes: a laminated body including a dielectric layer; a diplexer; a switching circuit; a low pass filter (LPF); a conductive pattern provided on the dielectric layer for forming at least one of the diplexer, the switching circuit and the LPF; a surface acoustic wave (SAW) filter mounted on the laminated body; a cover provided on the SAW filter for forming a cavity which allows surface acoustic wave vibration and for hermetically sealing the cavity; and a semiconductor switching device mounted on the laminated body for forming a part of the switching circuit.

THIS APPLICATION IS A U.S. NATIONAL PHASE APPLICATION OF PCTINTERNATIONAL APPLICATION PCT/JP01/08792.

TECHNICAL FIELD

The present invention relates to a radio-frequency hybrid switch modulefor use in mobile communications equipment including a mobile phone.

BACKGROUND ART

FIG. 1 is a circuit block diagram of an antenna duplexer used in aGSM/DCS dual-band mobile phone conforming to European standards formobile communications based on a Time Division Multiple Access system.The antenna duplexer includes antenna terminal 1, GSM-band transmitting(GSM-TX) terminal 2, GSM-band receiving (GSM-RX) terminal 3, DCS-bandtransmitting (DCS-TX) terminal 4, DCS-band receiving (DCS-RX) terminal5, diplexer 6 for separating and combining frequency components in GSMand DCS bands, switches 7, 8 for switching between transmission andreception, low pass filters (LPFs) 9, 11 for removing unwanted harmonicsignals, and surface acoustic wave (SAW) filters 10, 12 for allowing aband of received frequencies to pass.

FIG. 10 shows a structure of a conventional antenna duplexer. Thisantenna duplexer includes ceramic multi-layer substrate 18, aluminapackage 19, SAW device chip 20, bonding wire 21, lid 22 of aluminapackage 19, diodes 23 functioning as switching devices, chip devices 24,pad 25 formed on the alumina package for wire bonding, and metal cap 26.Ceramic multi-layer substrate 18 includes a LPF and a diplexer formedtherein.

In the duplexer described above, SAW chip 20 is put in alumina package19 and mounted over ceramic multi-layer substrate 18. Alumina package19, for being sealed hermetically with lid 22, needs to has a wallthickness 19 a ranging from about 0.5 mm to 1.0 mm, Thus hardly having areduced size.

DISCLOSURE OF THE INVENTION

A small radio-frequency (RF) hybrid switch module is provided forswitching between transmit-signals and receive-signals in pluralfrequency bands.

This module includes: a laminated body having a dielectric layer; adiplexer; a switching circuit; a low pass filter (LPF); a conductivepattern on the dielectric layer for forming at least one of thediplexer, the switching circuit and the LPF; a surface acoustic wave(SAW) filter mounted on the laminated body; a cover on the SAW filterfor forming a cavity which allows surface acoustic wave vibration andhermetically sealing the cavity, and a semiconductor switching devicemounted on the laminated body for forming a part of the switchingcircuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit block diagram of a radio-frequency (RF) hybridswitch module in accordance with first to fourth exemplary embodimentsof the present invention.

FIG. 2 is another circuit block diagram of an RF hybrid switch module inaccordance with the first to fourth embodiments.

FIG. 3 is a further circuit block diagram of an RF hybrid switch modulein accordance with the first to fourth embodiments.

FIG. 4 is a still further circuit block diagram of an RF hybrid switchmodule in accordance with the first to fourth embodiments.

FIG. 5 is a schematic diagram of an RF hybrid switch module inaccordance with the first embodiment of the invention.

FIG. 6 is a schematic diagram of an RF hybrid switch module inaccordance with the second embodiment of the invention.

FIG. 7 is a schematic diagram of another RF hybrid switch module inaccordance with the second embodiment of the invention.

FIG. 8 is a schematic diagram of an RF hybrid switch module inaccordance with the third embodiment of the invention.

FIG. 9 is a schematic diagram of an RF hybrid switch module inaccordance with the fourth embodiment of the invention.

FIG. 10 is a schematic diagram of a conventional antenna duplexer.

BEST MODES FOR CARRYING OUT THE INVENTION

First Exemplary Embodiment

FIGS. 1-4 are circuit block diagrams each illustrating a radio-frequency(RF) hybrid switch module for a GSM/DCS mobile phone conforming withEuropean standards for mobile communications. The module includes switch13 for switching between transmission and reception in GSM and DCSbands, diplexers 14, 15, low pass filters (LPFs) 9, 11 for removingharmonics, and SP4T switch 17.

In the circuit illustrated by FIG. 1, antenna terminal 1 is connected todiplexer 6 which separates and combines signals in the GSM and DCSbands. Respective terminals for the GSM and DCS bands of diplexer 6 areconnected to switches 7 and 8, respectively. Transmitting sides ofswitches 7, 8 are connected to LPFs 9, 11, respectively, while receivingsides of switches 7, 8 are connected to surface acoustic wave (SAW)filters 10, 12, respectively. Filters 9, 10, 11, 12 are connected toterminals 2, 3, 4 and 5, respectively.

In the circuit illustrated by FIG. 2, an antenna terminal is connectedto switch 13. Switch 13 separates signals into transmitted signals andreceived signals. Diplexers 14, 15 separate and combine the signals inthe GSM and DCS bands. Transmitting terminals of diplexer 14 areconnected to LPFs 9 and 11, respectively, while receiving terminals ofdiplexer 15 are connected to SAW filters 10 and 12, respectively.Filters 9, 10, 11, 12 are connected to terminals 2, 3, 4 and 5,respectively.

In the circuit illustrated by FIG. 3, LPF 16 for removing a harmoniccomponent from a transmitted signal is connected to antenna terminal 1.SP4T switch 17 allocates the transmitted signals and received signalsamong terminals 2, 3, 4, and 5. Receiving terminals of switch 17 arecoupled to terminals 3, 5 via SAW filters 10, 12, respectively.

In the circuit illustrated by FIG. 4, SP4T switch 17 is connected toantenna terminal 1. Transmitting terminals of switch 17 are connected toLPFs 9, 11, respectively, while receiving terminals of switch 17 areconnected to SAW filters 10, 12, respectively. Filters 9, 11, 10, 12 areconnected to terminals 2, 3, 4 and 5, respectively.

In the circuits described above, switches 7, 8, 13, 17 are each formedof a semiconductor switching device, e.g. a diode or a field effecttransistor. LPFs 9, 11, 16 and diplexers 6, 14, 15 are formed of aconductive pattern provided on a dielectric layer. This dielectric layerand other dielectric layer form a laminated body.

FIG. 5 shows an RF hybrid switch module in accordance with the firstembodiment. The module includes cover (hereinafter referred to as“micro-cavity”) 27 defining a cavity at an elastic vibrating portion ofSAW filter chip 20, potting resin 28, and pad 29 formed on laminatedbody 18 for wire bonding.

In the first embodiment, the elastic surface portion of SAW filter chip20 is formed with micro-cavity 27 and fortified with potting resin 28,thereby being hermetically sealed over laminated body 18 withoutinterfering an elastic vibration. Chip devices 23, 24 are mounted nextto chip 20.

Consequently, the module of this embodiment has a smaller size and alower profile than a conventional module and can be manufacturedinexpensively since this module does not require an alumina package.Further, The plate-like laminated body 18 may be divided into an areafor SAW filter chip 20 and an area for chip devices 23, 24, thusallowing only the area for the chip devices, for example, to havesoldering paste printed thereon, to be subjected to reflow, and to becleaned. This facilitates the chip devices to be mounted easily andenhances cost reduction of the module.

Second Exemplary Embodiment

FIG. 6 shows a radio-frequency hybrid switch module in accordance with asecond exemplary embodiment of the present invention. An elastic surfaceportion of SAW filter chip 20 is provided with micro-cavity 27, a coverdefining a cavity. Micro-cavity 27 is fortified with potting resin 28 asin the module shown in FIG. 5, thus allowing the elastic surface portionto be hermetically sealed over laminated body 18 without interferingwith elastic vibration. Bare-chip diode 30 is mounted on laminated body18 similarly to SAW filter chip 20 and coated with potting resin 28.

Therefore, the module of the present embodiment has a smaller size and alower profile than a conventional module and can be manufacturedinexpensively since this module does not require an alumina package.Further, plate-like laminated body 18 is divided into an area for SAWfilter chip 20 and an area for chip devices 23, 24 thus allowing onlythe area for the chip devices, for example, to have soldering pasteprinted thereon, to be subjected to reflow, and to be cleaned. Thisfacilitates the chip devices to be mounted easily and enhances costreduction of the module. The similar advantages are obtainable even if asemiconductor switching device, e.g. a field effect transistor, is usedinstead of bare-chip diode 30.

As shown in FIG. 7, wall 33 made of resin may be provided on theperiphery of the bare chips on the laminated body. Wall 33 is tallerthan the bare chips. The bare chips placed across wall 33 from the chipdevices may be covered with the potting resin. Thus, the potting resinis prevented from flowing into a region not requiring the potting resin,and a region to be covered with the potting resin is limited.Accordingly, a clearance for an overflowing potting resin can beminimized, and this reduces the size of the module easily and improvesproduction yield of the module.

Wall 33 may be formed next to chip devices 24 or may be formed toenclose the bare chips (including SAW filter chip 20 and bare-chip diode30 in FIG. 6).

As shown in FIG. 6, at least one of the SAW filter and the bare chip isdisposed on one side of the laminated body. In other words, the barechips are separated from the chip devices on the laminated body by beingdisposed in the area positioned in horizontal or vertical relation tothe area for the chip devices. This allows the module to be manufacturedsince soldering paste can be applied to laminated body 18 by thick filmprinting to solder the chip devices, and since flux can be cleanedefficiently after the soldering.

The potting resin may cover the entire surface of the laminated body onwhich the chips and the chip devices are mounted. This improvesmechanical reliability of the module. In addition, the module can bemanufactured easily and inexpensively since a region (not shown) to becoated with the potting resin need not be specifically restricted.

Third Exemplary Embodiment

FIG. 8 shows a radio-frequency (RF) hybrid switch module in accordancewith a third exemplary embodiment. The module includes bump 31 andsealing resin 32. Bump 31 functioning as an electrode for SAW filterchip 20 is electrically connected to a pad provided on laminated body 18by flip chip bonding. A space between SAW filter chip 20 and laminatedbody 18 is filled with sealing resin 32 for covering a connectionbetween bump 31 and the pad. This seals the periphery of this connectionhermetically without contacting cap 26. An elastic surface portion ofSAW filter chip 20 is provided with micro-cavity 27, a cover defining acavity similarly to the modules shown in FIGS. 5 and 6, thus beinghermetically sealed without interfering with elastic vibration at theelastic surface portion.

The RF hybrid switch module of the present embodiment has a smaller sizeand a lower profile than a conventional module, and can be madeinexpensively since this module does not require an alumina package.Further, plate-like laminated body 18 is divided into an area for SAWfilter chip 20 and an area for chip devices 23, 24, thus allowing onlythe area for chip devices, for example, to have soldering paste printedthereon, to be subjected to reflow, and to be cleaned. This facilitatesthe mounting of the chip devices and enhances cost reduction of themodule.

Fourth Exemplary Embodiment

FIG. 9 shows a radio-frequency (RF) hybrid switch module in accordancewith a fourth exemplary embodiment. In this module, bump 31 of SAWfilter chip 20 is electrically connected to a pad provided on laminatedbody 18 by flip chip bonding. A space between SAW filter chip 20 andlaminated body 18 is filled with sealing resin 32 for covering aconnection between bump 31 and the pad. The resin seals the periphery ofthis connection hermetically without contacting cap 26. An elasticsurface portion of SAW filter chip 20 is provided with micro-cavity 27and a cover defining a cavity similarly to the modules shown in FIGS. 5and 6, thereby being hermetically sealed without interfering withelastic vibration occurring at the elastic surface portion. Togetherwith the SAW filter chip, bare-chip diode 30 may be coated with sealingresin 32.

The RF hybrid switch module of the fourth embodiment has a smaller sizeand a lower profile than a conventional module and can be manufacturedinexpensively since this module does not require an alumina package.Further, plate-like laminated body 18 is divided into an area for SAWfilter chip 20 and an area for chip devices 23, 24, thus allowing onlythe area for chip devices, for example, to have soldering paste printedthereon, to be subjected to reflow, and to be cleaned. This facilitatesthe mounting of the chip devices and enhances cost reduction of themodule. The similar advantages can be obtained even when a semiconductorswitching, e.g. a field effect transistor, is used instead of bare-chipdiode 30.

In the first to fourth embodiments, a GSM/DCS dual-band device isexplained. However, the present invention is not limited to this and maybe applicable to, for example, single-band and triple-band devices.

The number of chip devices and the number of SAW filter chips that havebeen illustrated in the first to fourth embodiments do not restrict thetechnique of the present invention. The same advantages can be obtainedfrom, for example, a module including no chip device. In addition, themodule may not include cap 26.

The laminated body of the RF hybrid switch module in accordance witheach of the first to fourth embodiments may include a thin ceramicsubstrate previously sintered and smoothed at its surface to which theSAW filter is mounted. Specifically, plural yet-to-be-sintered greensheets are affixed to the ceramic substrate, and a conductive pattern isprinted on or transferred to the green sheet for forming a circuit. Theresultant laminated body is thereafter sintered and then having the SAWfilter mounted thereon. In this way, the SAW filter can be mounted tothe smooth surface of the previously-sintered ceramic substrate, andthis provides the module with extremely high reliability. Alumina,forsterite or the like is usable for the ceramic substrate. The greensheet, upon being made of material sintered at a low temperature, allowsmaterial having a low resistance, e.g. silver and copper, to be used forthe conductive pattern forming the circuit, and this reduces loss in thecircuit.

INDUSTRIAL APPLICABILITY

In a radio-frequency hybrid switch module of the present invention, anelastic surface portion for generating a surface acoustic wave isprovided with a cavity and is hermetically sealed. Thus, a surfaceacoustic wave filter can be mounted on a laminated body similarly toother chip devices. This allows the module to have an extremely smallsize and a low-profile.

What is claimed is:
 1. A radio-frequency (RF) hybrid switch modulecomprising: a laminated body including a dielectric layer; a diplexer; aswitching circuit; a low pass filter (LPF); a conductive pattern on saiddielectric layer, for forming at least one of said diplexer, saidswitching circuit, and said LPF; a surface acoustic wave (SAW) filtermounted on said laminated body; a cover on said SAW filter, for forminga cavity which allows surface acoustic wave vibration and forhermetically sealing said cavity; a semiconductor switching devicemounted on said laminated body, for forming a part of said switchingcircuit; a pad provided on said laminated body; a bonding wireconnecting said SAW filter to said pad; and a potting resin coveringsaid pad, said bonding wire, and said SAW filter.
 2. The RF hybridswitch module of claim 1, wherein said laminated body further includes aceramic substrate on which said SAW filter is mounted.
 3. The RF hybridswitch module of claim 1, wherein said semiconductor switching device isa bare chip, and wherein said potting resin covers said bare chip. 4.The RF hybrid switch module of claim 3, further comprising: a wallprovided at a periphery of said bare chip on said laminated body, saidwall being taller than said bare chip, wherein said potting resin coverssaid bare chip from said wall.
 5. The RF hybrid switch module of claim3, further comprising: a chip device included in at least one of saiddiplexer, said switching circuit and said LPF, said chip device beingmounted on said laminated body, wherein a position for at least one ofsaid SAW filter and said bare chip and a position for said chip deviceare mounted in respective two regions separated from each other on saidlaminated body.
 6. The RF hybrid switch module of claim 1, wherein saidpotting resin covers substantially an entire surface of said laminatedbody including said semiconductor switching device and said SAW filtermounted thereon.
 7. A radio-frequency (RF) hybrid switch modulecomprising: a laminated body including a dielectric layer; a diplexer; aswitching circuit; a low pass filter (LPF); a conductive pattern on saiddielectric layer, for forming at least one of said diplexer, saidswitching circuit, and said LPF; a surface acoustic wave (SAW) filtermounted on said laminated body; a cover on said SAW filter, for forminga cavity which allows surface acoustic wave vibration and forhermetically sealing said cavity; a semiconductor switching devicemounted on said laminated body, for forming part of said switchingcircuit; and a potting resin for covering substantially an entiresurface of said laminated body including said semiconductor switchingdevice and said SAW filter mounted thereon.
 8. The RF hybrid switchmodule of claim 7, wherein said laminated body further includes aceramic substrate on which said SAW filter is mounted.
 9. Aradio-frequency (RF) hybrid switch module comprising: a laminated bodyincluding a dielectric layer; a diplexer; a switching circuit; a lowpass filter (LPF); a conductive pattern on said dielectric layer, forforming at least one of said diplexer, said switching circuit, and saidLPF; a surface acoustic wave (SAW) filter mounted on said laminatedbody; a cover on said SAW filter, for forming a cavity which allowssurface acoustic wave vibration and for hermetically sealing saidcavity; a semiconductor switching device mounted on said laminated body,for forming a part of said switching circuit; a pad provided on saidlaminated body; a bump provided at said SAW filter for electricallyconnecting said SAW filter to said pad by flip chip bonding; and apotting resin with which a space between said SAW filter and saidlaminated body is filled for covering said pad and said bump.
 10. The RFhybrid switch module of claim 9, wherein said laminated body furtherincludes a ceramic substrate on which said SAW filter is mounted.
 11. Amethod of manufacturing a radio-frequency hybrid switch module includinga laminated body having a dielectric layer, a conductive patternprovided on the dielectric layer, and a surface acoustic wave (SAW)filter mounted on the laminated body, said method comprising the stepsof: forming the conductive pattern on a green sheet by one of printingand transferring; affixing the green sheet to a sintered ceramicsubstrate; sintering the ceramic substrate and the green sheet to formthe laminated body; and mounting the SAW filter on the ceramicsubstrate.